Wolbachia in the flesh: symbiont intensities in germ-line and somatic tissues challenge the conventional view of Wolbachia transmission routes

Symbionts can substantially affect the evolution and ecology of their hosts. The investigation of the tissue-specific distribution of symbionts (tissue tropism) can provide important insight into host-symbiont interactions. Among other things, it can help to discern the importance of specific transmission routes and potential phenotypic effects. The intracellular bacterial symbiont Wolbachia has been described as the greatest ever panzootic, due to the wide array of arthropods that it infects. Being primarily vertically transmitted, it is expected that the transmission of Wolbachia would be enhanced by focusing infection in the reproductive tissues. In social insect hosts, this tropism would logically extend to reproductive rather than sterile castes, since the latter constitute a dead-end for vertically transmission. Here, we show that Wolbachia are not focused on reproductive tissues of eusocial insects, and that non-reproductive tissues of queens and workers of the ant Acromyrmex echinatior, harbour substantial infections. In particular, the comparatively high intensities of Wolbachia in the haemolymph, fat body, and faeces, suggest potential for horizontal transmission via parasitoids and the faecal-oral route, or a role for Wolbachia modulating the immune response of this host. It may be that somatic tissues and castes are not the evolutionary dead-end for Wolbachia that is commonly thought

Sex Determination in Honeybees: Two Separate Mechanisms Induce and Maintain the Female Pathway

Sex determination in honeybees is realized by the csd and the fem gene that establish and maintain, throughout development, sexual fates via the control of alternative splicing

The Dynamics of Plant Cell-Wall Polysaccharide Decomposition in Leaf-Cutting Ant Fungus Gardens

The degradation of live plant biomass in fungus gardens of leaf-cutting ants is poorly characterised but fundamental for understanding the mutual advantages and efficiency of this obligate nutritional symbiosis. Controversies about the extent to which the garden-symbiont Leucocoprinus gongylophorus degrades cellulose have hampered our understanding of the selection forces that induced large scale herbivory and of the ensuing ecological footprint of these ants. Here we use a recently established technique, based on polysaccharide microarrays probed with antibodies and carbohydrate binding modules, to map the occurrence of cell wall polymers in consecutive sections of the fungus garden of the leaf-cutting ant Acromyrmex echinatior. We show that pectin, xyloglucan and some xylan epitopes are degraded, whereas more highly substituted xylan and cellulose epitopes remain as residuals in the waste material that the ants remove from their fungus garden. These results demonstrate that biomass entering leaf-cutting ant fungus gardens is only partially utilized and explain why disproportionally large amounts of plant material are needed to sustain colony growth. They also explain why substantial communities of microbial and invertebrate symbionts have evolved associations with the dump material from leaf-cutting ant nests, to exploit decomposition niches that the ant garden-fungus does not utilize. Our approach thus provides detailed insight into the nutritional benefits and shortcomings associated with fungus-farming in ants

Random and channeled energy loss in thin germanium and silicon crystals for positive and negative 2-15-GeV/c pions, kaons, and protons

Energy loss of 2-, 6-, and 15-GeV/c positive and negative protons, kaons, and pions transmitted through thin germanium and silicon crystals are measured using the crystałs as intrinsic detectors. For particles incident in directions far from axial or planar directions the results are in accord with the relativistic Bethé-Bloch stopping theory. The density effect plays an important role at these energies. The spectral distribution of energy losses is in good agreement with the Landau distribution. For positive particles aligned with an axis or a plane, the energy loss is considerably reduced compared to random. The measurements agree well with theoretical calculations. Negative particles, well aligned to a crystal axis, show increased energy loss compared to random by as much as ∼20%.Physic

Contribution from close and distant collisions to K-shell excitation in Ge measured using the channeling technique for relativistic protons, π+\pi^{+}, and π−\pi^{-}

For the first time, the impact-parameter dependence for K-shell ionization was measured for relativistic projectiles, although in an indirect way. Experimentally, channeling of GeV projectiles was used to gradually exclude close-encounter processes. In the present experiment, the Lorentz gamma factor varied between approximately 2 and approximately 100; in this region, the contribution from distant collisions becomes increasingly important and amounts to about 50% of the total yield for gamma approximately 100. The experimental data are compared to theoretical calculations of impact-parameter distributions, and the agreement is fair for both positive and negative particles